Metallographic examination originated with Aloys Beck von Widmanstätten and gained recognition through the work of Professor Henry C. Sorby in the late 19th century. It involves the microscopic study of the structural characteristics of metals and alloys, focusing on grain size, shape, and phase distribution. Modern metallurgical microscopes utilize light reflection to analyze samples, achieving magnifications of up to 2000x, and can include features for photographic documentation of findings.

1. INTORODUCTION
 The credit for originating Metallographic
examination goes to Aloys beck von
Widmanstatten (between 1808 and 1840).
 Microscope was employed for the purpose in 1841,
when Paul Annosow used the instrument to
examine the etched surface of oriental steel blades.
 It was around 1890 when metallography technique
received general recognition, largely as a result of the
work of professor Henry C. Sorby in England.

2.  Metallography consist of the microscope study of the
structural characteristics of a metal or an alloy.
 Metallography is the general study of metal and their
behavior , with particular reference to their microstructure and
macrostructure.
 A metallurgical microscope helps determining:
-- Grain size and shape.
-- Size, shape and distribution of various phase and
inclusion.
--Mechanical and thermal treatment of the alloys.

4.  All using the principle of examination
by the reflection of light from the
specimen surface.

5.  A draw tube carrying eyepiece at its top end slides with in the
body tube of the microscope , with the help of a rack and pinion
device by rotating coarse and fine adjustment knobs.
 Sliding of draw- tube within the body tube varies the distance
between the eyepiece and the objective and thus helps focusing the
object.
 Fine the objective, fitted at the down end of the body tube, resolves
the structure of the metal (specimen) whereas the eyepiece larges
the image formed by the objective.
 Eyepieces made in a variety of Powers, such as X5, X8, X10, etc.,
marked on the top of the eyepiece.
 The source of light is inside the microscope tube itself.

7.  Light is diffused with the help of a diffusing disc. The width of the
light beam is controlled by the iris diaphragm disc.
 the incident light strike the plane glass reflector kept at 45 and is
partially reflected down onto the specimen. The rays of light get
returned by reflection from the (polished) specimen, pass through
the objective and glass reflector to from the final image which can
be seen through the eyepiece.
 A photographic camera may be mounted above the eyepiece in
order to record permanently the metallographic structure of the
alloy.
 The maximum magnification obtain with the optical microscope is
about 2000X.

8. O.P. KHANA BOOK – Material science and metallurgy
Chapter – 42(Metallography)

9. any
question